docs: def del_avatar(self, a, b=None):
          """This is no longer my avatar, though it still exists on its own."""
          if self.engine._planning:
              raise NotImplementedError("Currently can't remove avatars within a plan")
          if b is None:
              if not isinstance(a, Node):
                  raise TypeError(
                      "In single argument form, "
                      "del_avatar requires a Node object "
                      "(Thing or Place)."
                  )
              g = a.character.name
              n = a.name
          else:
              g = a.name if isinstance(a, Character) else a
              n = b.name if isinstance(b, Node) else b
          self.engine._remember_avatarness(
              self.character.name, g, n, False
          )